Search

We describe the pulse generation, shaping, and preamplification system for the nanosecond beamlines of the Orion laser facility. The system generates shaped laser pulses of up to N1 J of 100 ps-5 ns duration with a programmable temporal profile. The laser has a 30th-power supergaussian spatial profile and is diffraction limited. The system is capable of imposing 2D smoothing by spectral dispersion upon the beam, which will produce a nonuniformity of 10% rms at the target. OCIS codes: 140.3280, 140.3530, 030.6140.

Blumlein pulsers are well-suited devices for high-voltage pulse generation in nanosecond and microsecond ranges. These generators have been used with great success in several areas such as in breakdown tests, X-ray generation, lasers, and high-energy plasma implantation. They consist of lengths of transmission lines charged in parallel and synchronously discharged in series into the load by using single or multiple switches at the opposite line endings. The main problem with the device performance is the presence of the shield cable impedance contributing to the Blumlein power loss especially when using only one switch. The very well known technique used for minimizing these losses consists of winding the transmission lines to increase the line shielding inductance if coaxial cables are used. Therefore, herein, circuit models are presented to assess theoretically the temporal response of the wound coaxial Blumlein pulsers by using a SPICE circuit simulator. For model assessment, the authors used the experimental results produced by a wound coaxial Blumlein pulser of 100 kV/200 A with 1.0 [micro]s of pulse duration constructed for applications in surface treatment of polymers and aluminum with high-energy ions. Index Terms--Blumlein, coaxial cable, modeling, pulser, SPICE simulator, transmission line.

To study the performance of compact systems for microwave generation, a series of experiments have been performed with a microwave source powered directly by a Marx generator. The system consists of a 20-stage 400-kV/400-J Marx generator, a powerful 40-kV charger, a reflex triode, and a vircator-type microwave source. Different parametric studies were performed such as variation of the anode-cathode distances and the emitting area of the cathode. The results have been analyzed and compared to an equivalent electric circuit model of the system. The experiments, generating microwave frequencies between 3 and 5 GHz, can be fairly accurately reproduced by the model both in terms of discharge currents and microwave frequencies. Index Terms--Electron beams, Marx generators, microwave generation, pulsed power systems.

This paper describes the design, construction, and testing of a digital versatile disc (DVD) based electronic pulser system (DVDEPS). Such a device is used to generate pulse streams for simulation of both gamma and neutron detector systems. The DVDEPS reproduces a random pulse stream of a full high purity germanium (HPGe) spectrum as well as a digital pulse stream representing the output of a neutron multiplicity detector. The exchangeable DVD media contains over an hour of data for both detector systems and can contain an arbitrary gamma spectrum and neutron pulse stream. The data is written to the DVD using a desktop computer program from either real or simulated spectra. The targeted use of the DVDEPS is authentication or validation of monitoring equipment for non-proliferation purposes, but it is also of general use in a variety of sitiuations. The DVD based pulser combines the storage capacity and simplicity of DVD technology with commonly available electronic components to build a relatively inexpensive yet highly capable testing instrument. Index Terms--Pulse generation, radiation detector circuits.

A prospective module has been designed for a future large inductive voltage adder (IVA) machine that would be suitable for the most demanding radiography carried out at AWE Aldermaston, Berkshire, U.K. This machine would operate at 13-15 MV. The prototype IVA module (PIM) machine has been built to test a single such module and may also provide the basis for other, lower voltage machines in the future. It consists of a single inductive cavity pulsed by a 10-[OMEGA] water dielectric Blumlein pulse forming line which is charged by a Marx generator. The Blumlein switch initially installed was a coaxial two stage Rimfire and Trigatron switch. A laser triggering configuration utilizing two radial switches, designed by Titan PSI, is also to be tested. The Blumlein PFL and its switch were tested using a copper sulphate resistive load and achieved a peak output voltage of 1.7 MV. The inductive cavity has been added and a pulse of 1.5-MV peak voltage has been successfully applied to it. Index Terms--Blumlein, inductive voltage adder (IVA), Metglas, radiography.

A pulse generator of a one-stage magnetic pulse compression (MPC) modulator, which has an average power of 7.5 kW, was developed. The modulator consists of a constant-current capacitor charger (max. 21.7 kV, 300 Hz), an initial charge capacitor (0.2 [micro]F, 40 kV), a thyratron switch, a pulse transformer with a turn ratio of 1 to 8, ceramic capacitors (2.7 nF, 160 kV), and a magnetic switch. The output voltage, current and the pulsewidth of the modulator were measured to be 85.6 kV, 1.88 kA, and 200 ns (full width half maximum) respectively, with the initial charging voltage of 20 kV. This modulator system can be operated at the maximum repetition rate of 300 Hz and the energy delivery efficiency from the initial charge capacitor to the dummy load is estimated as 55%. The pulse generator is applied to a reactor of pin-to-hole type to investigate the impedance matching between the pulse generator and the reactor, and the experimental results are presented. Index Terms--Impedance matching, N[O.sub.x], pulse generator, reactor.

Presented are theoretical and experimental results from a project supporting development of a new method for cement vibration in well' s annulus to prevent gas migration. In this method, cyclic pressure pulses are applied at the wellhead and transmitted down the annulus. These pulses cause reciprocation and shear within cement column - a process delaying the loss of hydrostatic pressure and preventing the inflow of gas into the well's annulus. Field tests in real wells conducted to observe transmission of a single pressure pulse and to measure compressibility of setting cement showed that application of pressure pulses of 100 psi amplitude and 0.1 Hz frequency may be an effective and inexpensive way of preventing gas flow after cementing. The paper presents development of a cement pulsation design method based upon the analytical model of pressure propagation in Bingham plastic fluid and experimental data on rheology of cement slurries subjected to continuous shear. The primary objective of the method is to minimize the likelihood of gas invasion into the cement-filled annulus.

An experiment was conducted to determine the accuracy of charge-pumping measurement technique with gate sawtooth pulses on metal oxide semiconductor field effect transistors. A pulse generator was utilized to supply the gate sawtooth pulses and a reverse bias method was applied to the source and drain of the transistors. Results revealed that the dominant mechanism which affected the measurement accuracy was the energy range of interface-trap distribution.

The development and experimental investigation of a large-current radiator (LCR) with a pulse generator using avalanche transistors is reported. The LCR is intend for radiating nonsinusoidal pulse electromagnetic waves with a duration of 2 ns. The radiated field strengths in both the near and the far field are measured. The LCR described produces magnetic field strengths of about 4.2 mA/m at a distance of 5 m for radiator current amplitudes of about 0.7 A with rise time of 1 ns. The width of the antenna pattern, measured by the drop of the field strength to one half of its peak value is 120 [degrees]. Index Terms - Avalanche transistor, far-field, large-current radiator, near-field, nonsinusoidal waves.

A configuration using a polarization-mismatching model with time delay achieves a high tripling conversion efficiency of 75% for a picosecond laser pulse at the intensity of 6 gigawatts/cm squared. The optimum conditions are an intensity ratio of 2, time delay of 0.8 picosecond, doubler and tripler thickness of 1 cm, and polarization angle of 54.7 degrees. The tripling conversion efficiency for high intensities above 75 gigawatts/cm squared can be as high as 80%.

A new phase noise reduction technique has been developed for PLL frequency synthesizers. The key circuit elements have been fabricated in one LSI, and applied to a C-band MMIC frequency synthesizer. The resultant phase noise reduction of 10 dB is significant.

A novel method is presented of using waveform-generators for generating the sine pulsewidth modulation (PWM) control signals for a bridge inverter. The frequencies of the reference sine and synchronized triangular waveforms needed for PWM can be varied simultaneously over a wide range. Experimental waveforms of control circuit and inverter are given.

One of the key problems in the development of high power ion diodes is the formation of a suitable anode plasma source layer. To provide an ion current density of up to 10 kA/cm squared for a pulse duration of 50 ns, a minimum of 3 center dot 10 to the fifteenth power ions/cm squared is needed. This layer should uniformly cover an area of more than 100 cm squared and smoothly conform to the desired anode shape without any protuberances into the accelerating gap. We have developed a scheme for the active production of a proton source layer meeting these requirements which is based on a thin metal-hydride film. A 500 angstroms thick Ti-layer is used as the hydrogen store. It is covered with a 100-300 angstroms thick Pd-layer to prevent oxidation of the Ti-surface. A fast heating pulse desorbs a large fraction of the hydrogen within a few ns from the metal-hydride. After a sufficient amount of gas has been released an electrical discharge is initiated in the gas layer to create the plasma. The paper describes the dynamics of hydrogen desorption and of plasma layer formation. Experimental investigations have been conducted to determine the characteristics of the discharge and to measure the plasma parameters. Since the plasma is far from thermodynamic equilibrium spectroscopic methods with high spatial and temporal resolution have been applied. Using this ion source in a TW diode installed at the high power pulse generator KALIF an intense high brightness proton beam of 0.64 TW power and 50 kJ pulse energy has been created.

A scheme for a high-current high-di/dt pulse generator is described, which incorporates an assembly of reverse switching dynistors (RSDs), a magnetic compression section, a trigger circuit based on a step-up saturable pulse transformer, and an additional RSD unit with a small working area. The generator, with an operating voltage of 10 kV, can switch a 108-kA pulse current with a full width at half maximum of about 65-[micro]s duration, a di/dt of 8.66 kA/[micro]s, and a jitter of less than 60 ns. The charge transferred and action are about 6 C and 0.53 [MA.sup.2]s, respectively. Index Terms---di/dt, pulse generator, reverse switching dynistor (RSD), saturable transformer.

A short duration of 100-ns pulsed power has been used to remove nitric oxide (NO) in a mixture of nitrogen, oxygen, water vapor, and NO, simulating flue gases from a power station. The effects of the gas flow rate, the reactor length, and the pulse repetition rate on the percentage of NO removal and its energy efficiency are reported. The percentage of NO removal at a fixed gas flow rate increased with increasing pulse repetition rate due to the increased energy into the discharge. At a fixed pulse rate, the removal of NO increased with decreasing gas flow rate due to the increased residence time of the gas in the discharge reactor, thus facilitating the creation of increased radicals of O and N which then decreased NO. The energy removal efficiency of NO (in mol/kWh) decreased with increasing gas flow rate and increasing removal ratio of NO. The removal of NO increased with increasing energy density (J/I) input into the discharge at different reactor length. Index Terms--Coaxial reactor, energy efficiency, flue gases, [NO.sub.x] removal, pulsed power.

Using an improved pulsed electroacoustic (PEA) system which is capable of measuring space charge distribution at minimum intervals of 25 [micro]s, the charge distribution inside water-treed polyethylene (PE) was examined. From the results, the frequency dependencies of conductivity and permittivity were examined for water trees grown in PE. The conductivity of the water-treed region is found to be [is greater than][10.sup.10]x higher than that of non-treed regions, while the permittivity increase is only slight.

Scientists at Rice University, Houston, pioneered a tabletop magnetic pulse generator that reportedly does the work of a room-sized machine. RAMBO (Rice advanced magnet with broadband optics) allows researchers to [...]